An antagonistic bacterial strain GZA12 against soft rot of konjac:isolation,identification,and application in disease prevention and growth promotion

Abstract:

[Objective] Soft rot is one of the major diseases affecting the yield and quality of konjac.This study screened a strain with antagonistic effect on Pectinobacterium aroidearum from the rhizosphere soil of konjac,aiming to provide germplasm resources for the biocontrol of soft rot in konjac.[Methods] An antagonistic strain was screened by the plate confrontation method,and its antagonistic effects on pathogenic fungi were measured.The control effect of GZA12 on soft rot in konjac was examined by the inoculation in konjac corm tissue,pot experiment,and root irrigation.The growth-promoting effect of this strain was tested indoors and preliminarily verified by tomato pot experiments.[Results] A strain GZA12 with antagonistic effect was screened out and identified as Bacillus velezensis.This strain showed the inhibition zone diameter of 21.33 mm against P.aroidearum and the inhibition rates of 58.16%,47.30%,and 54.53% against Botryosphaeria dothidea,Fusarium oxysporum,and F.solani,respectively.Inoculation of GZA12 in konjac corm tissue decreased the disease index by 26.67%,33.33%,and 40.00%,respectively,compared with the inoculation of B.dothidea alone.In the pot experiment,the treatment with GZA12 suspension decreased the disease index by 22.85% compared with the control group and reached the control effect of 53.31%.The results from the root irrigation experiment showed that compared with water irrigation,irrigation with GZA12 fermentation broth reduced the disease index by 4.89% and reached the control effect of 21.57%.Strain GZA12 had the ability to fix nitrogen,solubilize phosphorus,and produce siderophores and indole-3-acetic acid (IAA).Inoculation with GZA12 suspension promoted the growth of tomato seedlings in a concentration-dependent manner.[Conclusion] Strain GZA12 can inhibit the pathogen causing soft rot and promote the growth of konjac,demonstrating the potential for further development and utilization.

Key words:Amorphophallus konjac;soft rot;Bacillus sp.;plant growth-promoting rhizobacteria;antagonism;growth promotion